Brian Ray

Guidelines for Selection of Speed Reduction Treatments at High-Speed Intersections

This study evaluated the effectiveness of treatments to reduce vehicle speeds at high-speed intersections. The treatments included geometric design features as well as signage and pavement markings. In the first phase of research, potential treatments were evaluated based on their applicability, key features, speed effects, safety benefits, multimodal impacts, and maintenance issues. The most promising treatments were evaluated using field testing at 10 sites in Oregon, Washington, and Texas. These guidelines are based on the research results and will provide highway planners and designers with an important new tool in their ongoing efforts to improve safety on the nations highway systems.

Evaluating the Performance of Corridors with Roundabouts

Roundabouts are increasingly recognized as an intersection control strategy that can fulfill multiple performance goals related to traffic operation and safety, as well as meet societal goals related to sustainability, livability, complete streets, context sensitive design, economic development, and others. Some transportation agencies have recently constructed or approved the use of a series of roundabouts on an arterial rather than the traditional solution of coordinated signalized intersections. While there are anecdotal reports suggesting that functionally interdependent roundabouts on a corridor are successful in meeting performance goals, little research has been conducted to determine objectively the efficacy of this alternative as compared to signalized intersections. This report provides performance measurement and evaluation methods, including a predictive model for travel speed and an overarching comparison framework, for comparing the performance of a corridor with a functionally interdependent series of roundabouts to a corridor with signalized intersections in order to arrive at a design solution. For the purposes of this research, a “series of roundabouts” is defined as at least three roundabouts that function interdependently on an arterial. These evaluation methods will be of use to traffic engineers and transportation planners.

Performance-Based Analysis of Geometric Design of Highways and Streets

For both new construction and reconstruction of highways and streets, stakeholders and decision makers increasingly want reasonable measures of the effect of geometric design decisions on the facility’s performance for all of its users. Although the expected performance of the facility is only one of the factors that must be considered in designing a highway or street, a better understanding of the expected performance should result in better decisions during the design process. This report presents ways to incorporate performance-based analysis into the project development process. This process framework begins with setting desired project multimodal outcomes and design controls. Geometric design decisions that can influence those outcomes are identified as well as analysis tools that can be used to estimate the impacts of those decisions. The report includes six project examples illustrating how this framework can be applied to actual projects. The report will be useful to geometric designers in making informed decisions about the tradeoffs inherent in design.